The present invention is directed in general to an apparatus and method for controlling operation of a remote locomotive in a train consist including a lead locomotive and one or more remote locomotives, and more specifically to such a method and apparatus for controlling remote locomotive operation when the remote locomotive is not in radio communication with the lead locomotive.
A radio-based control system for trains having a lead unit and one or more remote units (or groups of remote units) in which the control functions of the remote units are controlled by radio command signals from the lead unit is know in the art. Generally, this system is referred to as communication-based distributed power train control. The terminology xe2x80x9cunitxe2x80x9d as used herein describes a single diesel/electric locomotive, a group of adjacent diesel/electric locomotives, a single electrically-driven power provider, a group of adjacent electrically driven power providers, a single control car and a group of adjacent control cars, where the control cars do not supply driving power to the train but are used to control power providers. The control functions transmitted from the lead unit to the one or more remote units generally include the throttle setting (also referred to as the throttle notch position), air brake (also referred to as the pneumatic brake) setting (handle position), and the dynamic brake setting (dynamic step position). As is known by those skilled in the art, the air brake setting is also communicated to the remote units by the brake pipe pressure.
The one or more remote units can be controlled independently or synchronously. In one embodiment of the communication-based distributed power train control system, the operator can segregate the combination of all the powered units, including the lead unit and the remote units into a front group and a back group. The dividing line between the front group and the back group is determined by the position of a slider under control of the locomotive operator. For example, if the train includes a lead unit, a first remote unit, and a second remote unit, the locomotive operator can define the front group as comprising the lead unit and the first remote unit, while the back group comprises the second remote unit. Altenatively, the locomotive operator can position the slider to define the front group as including only the lead unit, while the back group includes both the first and second remote units. The independent mode is operative to control the front group independently from the back group, as determined by the slider position. The locomotive operator can also define the front group to include the lead units and both the first and second remote units. In this configuration, the communication-based distributed power train control system is operating in the synchronous mode. In the independent mode the train operator in the lead unit individually commands and controls the back group to a different throttle or brake setting by way of a signal transmitted over the communications channel. For example, the independent control mode may be used when the train is descending a long grade. As the lead unit approaches the grade, the train operator will slow down the lead unit white retaining the back group in its previous throttle position. As the back group reaches the crest, the operator throttles down the back group using the communications-based distributed power train control system. The operator will apply the dynamic brakes on the back group as it descends. Finally, when both groups return to level track, the system is returned to the synchronous mode so that both groups are controlled identically. In the synchronous mode, the lead and remote units respond to the same signal on the control channel and thus are set to the same throttle, air brake or dynamic brake setting. Each remote unit also provides a acknowledgement response to the lead unit over the communications channel. In addition, alarm conditions that occur on a remote unit are brought to the attention of the lead-unit operator over the communications channel. Further details of a communications-based distributed power train control system as described above can be found in U.S. Pat. No. 5,039,038 or U.S. Pat. No. 4,582,280. In another embodiment of the communications-based distributed power train control system, the lead and remote units do not necessarily have to be divided into a front group and a back group, but rather each lead unit and remote unit can be independently controlled by appropriate communication signals from the lead unit.
Obviously, when a radio link cannot be established between the lead unit and the one or more remote units, the lead unit is unable to control the operation of the remote units. Loss of this radio link occurs when the train passes through a tunnel or when buildings, hills, or other topographical or man-made features obstruct the line of sight between the transmitting antenna and the receiving antennas. The locations along the railway where communications will be lost are generally known in advance by the train operator who can therefore appropriately set the remote unit (or back group) controls before communications is lost. In fact, in some situations the loss of communications may not be detrimental, as the train air brake system alone can provide sufficient control over the remote units while the communications channel is inoperative. For example, assume the train is travelling through a tunnel with a relatively steep descent beginning midway through the tunnel. When the lead unit reaches the crest of the descent, the operator will throttle back the lead unit to slow the train. Because radio communications are disrupted in the tunnel, the remote units will continue to operate at their previous throttle setting. The communications-based distributed power train control system includes a timer feature to log the time interval between messages from the lead unit. That is, in one embodiment, the time interval is set at 45 seconds. A timer in the remote units is activated at the conclusion of a communications message from the lead unit. If the 45 seconds times out before the receipt of another message, then the lead units automatically begin to gradually throttle down from their current throttle notch position to the idle position.
Notwithstanding the timer feature, as the train descends through the tunnel, its speed increases and the operator applies the air brake to reduce the train speed. Although there is no communications link to the remote units, the air brake application at the lead unit is transmitted to the remote units via the brake pipe and therefore the remote units will also begin air brake application. The operator can then utilize the dynamic brake system on the lead unit to further adjust the train speed. In this scenario the lack of radio communication between the lead and remote units is not detrimental as adequate train control can be maintained, without radio communications.
Consider the case of a train entering a tunnel where the tunnel has a relatively steep ascent. If both the lead and remote unit throttles cannot be set to a higher notch position as each powered unit reaches the ascent, the train will be unable to climb the hill. The loss of communications in this scenario results in a stalled train. To overcome this disadvantage, tunnels are equipped with one or more repeater units placed proximate the track for receiving and re-transmitting the communications signal. A signal to increase the throttle notch position, for example, is received by the repeater and transmitted to the remote units. Generally, the tunnels are lined with leaky coaxial cable for use as the radiating element. Because the repeaters and leaky coax are expensive to install and maintain, it is desirable to seek a low cost solution, while providing remote unit control in the absence of a radio link between the lead unit and the remote units.
Thus, there is a particular need to provide for the control of locomotive remote units during transit over certain railway topographies where a communications link cannot be established between the one or more remote units and the lead unit. According to the teachings of the present invention, transponder devices are placed between the rails or along the track wayside to provide control information as a remote unit (or a lead unit) with a reading device passes over or proximate the transponder.